This invention deals with a drug, bio-affecting and body-treating type of compound. More specifically, this invention is concerned with the levulinic acid addition salt of 4-amino-6,7-dimethoxy-2-[4-(5-methylthio-1,3,4-oxadiazole-2-carbonyl]piper azin-1-yl)quinazoline containing a base to acid ratio of 1 to from 1.25-1.35. The free base form of the instant compound is also referred to herein by code number BL-5111 and is represented by the following structural formula. ##STR1##
Partyka, et al., U.S. Pat. No. 4,001,238 describe preparation of BL-5111 and its use as an antihypertensive agent. As stated therein, BL-5111 may be used for antihypertensive purposes as the free base or in the form of pharmaceutically acceptable acid salts thereof. Specifically, U.S. Pat. No. 4,001,238 at column 10, lines 12-13, discloses that salts of sulphuric acid, hydrochloric acid, succinic acid, tartaric acid, and benzoic acid are operable.
When a substance is employed for medical purposes, it is recognized that solubility of the therapeutic agent often is the controlling factor in determining route of administration and dosage forms. For instance, a water-soluble substance can be generally administered intravenously whereas a water-insoluble material is limited to other forms of parenteral administration such as intramuscular and subcutaneous. Since most parenteral products are preferably prepared as solutions, a therapeutic agent having water solubility likewise facilitates preparation of oral and various parenteral dosage forms for human administration. Thus, it is decidedly advantageous if a therapeutic agent is water-soluble and suited for parenteral administration particularly when one considers that the most direct route for achieving therapeutic blood levels of a drug within the human body is by intravenous administration.
Accordingly, the primary object of the present invention is to provide a water-soluble, stable, therapeutically acceptable form of the antihypertensive agent BL-5111 which can be administered both orally and intravenously as well as by other parenteral routes. This object as well as other features and advantages of the invention will be readily apparent to those skilled in the art from the disclosure set out below and accompanying claims.